/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineSessionInterface.h
Unregisters a group of players with the online service as being part of the online session
true if the call succeeds, false otherwise
bool UnregisterPlayers ( [FName](API\Runtime\Core\UObject\FName) SessionName, const [TArray](API\Runtime\Core\Containers\TArray)< FUniqueNetIdRef > & Players )